The invention relates to a crankcase venting system for an internal combustion engine including a partial load venting line leading to an engine intake duct downstream of a throttle valve of an engine intake system and a full load venting line connected to the engine intake duct upstream of the throttle valve.
Such a crankcase venting system is disclosed for example in DE 38 24 791 A1. The crankcase ventilating system described therein includes a main venting passage leading to the intake duct in the throttle valve housing and by way of a main throttling passage, an auxiliary venting passage which is arranged downstream the throttle valve and which is also a throttling passage and a venting line extending from the engine to the throttle valve housing. In order to prevent the development of ice at the throttle valve by the formation of condensate in the mixing area of fresh air with venting gases, the throttle valve housing is in communication with the cooling circuit so as to be heated thereby.
It is however a disadvantage of this arrangement that it requires a relatively complicated and expensive heating arrangement for the throttle valve housing in order to prevent the formation of ice therein. And in any case, ice formation in the throttle valves is prevented only when the engine is running since the throttle valve is not heated when the engine is shut down.
For general technical background information, reference is further made to DE 37 26 332 C1 and DE 19 16 788 C3.
It is the object of the present invention to provide a crankcase venting system for an internal combustion engine which insures sufficient venting of the engine crankcase under all engine operating conditions and wherein at the same time ice formation at the throttle valve is prevented without any additional special measures.